People have failed to ask which ftp service is being used
proFTPd or wu-ftpd
I would choose proFTPd it has an easier configuration.
f you are using proftp, try adding the line below in your /etc/proftpd.conf file:
DefaultRoot ~
That should set the users home directory to be the root of the file system for them to use. Also, they can only access other areas if the permissions are set to allow the request for the world. Or a group if they are assigned to the group. When you create the user/group set the home directory to there domain.
Also hopefully you just didnt uncomment out the port.
Here is a good site that has good refference
Guide The page is well done I used it as a refernce for Samba and my proFTpd. works very well and easy to understand